The proposal is directed at an extension of our findings related to antisera with apparent specificity for determinants on SLE mononuclear cells. An attempt will be made to extend immunochemical physical studies of the properties of antigens reacting with antisera prepared against mononuclear cells from patients with active SLE. After extensive adsorption and pepsin digestion, absorbed anti-SLE reagents will be utilized to further characterize antigens reactive with these antisera which are present on peripheral blood lymphocytes as well as polymorphonuclear leukocytes. A second portion of the study will focus on attempts to learn more about idiotypic antigens associated with rheumatoid factors in patients with rheumatoid arthritis. Analysis of cross reacting rheumatoid factors which react, not only with the Fc portion of IgG but also with nuclear antigens, will be extended and attempts will be made to utilize anti-rheumatoid factor idiotypic antibody to identify rheumatoid factor idiotypes or materials cross reacting with the latter in body fluid, urine and synovial tissue from patients with rheumatoid arthritis. Our attempts to prepare reagents capable of identifying T cell subclasses in peripheral blood and tissues (particularly T alpha and T mu cells) will be extended. These antisera will be prepared against isolated T gamma cells obtained from human cord bloods after extensive absorption with T mu cells, human thymocyte suspensions, and a number of other cell types. Similar approaches toward preparation of antisera for other T cell subsets, including T mu will be initiated. Finally, we will attempt to study the relationship between C-reactive protein (CRP) binding lymphocytes and cells capable of reacting with streptococcal antigens in acute rheumatic fever. These studies are designed to explore whether CRP is capable of modulating a potentially harmful immune response in this circumstance.